package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.sql.Time;
import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
        //互斥锁解决缓存击穿
//        Shop shop = queryWithPassThrough(id);
//        if(shop==null){
//            Result.fail("店铺不存在");
//        }

        //解决缓存穿透
       // Shop shop = queryWithMutex(id);
        //Shop shop = cacheClient.queryWithMutex(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);

        //逻辑过期解决缓存击穿问题
        //Shop shop =queryWithLogicalExpire(id);
       Shop shop = cacheClient.queryWithLogicalExpire(LOCK_SHOP_KEY,CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL, TimeUnit.MINUTES);

     return Result.ok(shop);

    }



    public Shop queryWithPassThrough(Long id){
        String key = CACHE_SHOP_KEY+id;
        //1.从redis查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson,Shop.class);
            return shop;
        }

        if(shopJson==""){
            return null;
        }

        //实现缓存重建
        //获取互斥锁
        String lockKey = LOCK_SHOP_KEY+id;
        Shop shop = null;
       try {
           boolean islock = tryLock(lockKey);
           //判断是否获取成功
           if(!islock){
               //失败，休眠并重试
               Thread.sleep(50);
               return queryWithMutex(id); //重新尝试获取
           }

           //4.不存在，根据id查数据库
            shop = getById(id);

           //5.不存在，返回错误
           if(shop==null){
               stringRedisTemplate.opsForValue().set(key,"",CACHE_SHOP_TTL, TimeUnit.MINUTES);
               return null;
           }
           //6.存在写入redist,30分钟自动过期
           stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
       }catch (InterruptedException e){
           throw  new RuntimeException();
       }finally {
           //释放锁
           unlock(lockKey);
       }

        //7.返回
        return shop;
    }

    public Shop queryWithMutex(Long id){
        String key = CACHE_SHOP_KEY+id;
        //1.从redis查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson,Shop.class);
            return shop;
        }

        if(shopJson==""){
            return null;
        }

        //4.不存在，根据id查数据库
        Shop shop = getById(id);

        //5.不存在，返回错误
        if(shop==null){
            stringRedisTemplate.opsForValue().set(key,"",CACHE_SHOP_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在写入redist,30分钟自动过期
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //7.返回
        return shop;
    }

private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public Shop queryWithLogicalExpire(Long id){
        String key = CACHE_SHOP_KEY+id;
        //1.从redis查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(shopJson)){
            //不存在直接返回
            return null;
        }
        //命中，把json转化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject)redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //命中，需要判断过期时间
        if(expireTime.isAfter(LocalDateTime.now())){
            //未过期，直接返回
            return shop;
        }


        //过期，需要重建
        //获取锁
        String lockkey =  LOCK_SHOP_KEY+id;

        boolean flag = tryLock(lockkey);
        if(flag){
            //成功，开启新线程，实现重建
              CACHE_REBUILD_EXECUTOR.submit(()->{
                 //重建
                  try {
                 this.saveShop2Redis(id,20L);
              }catch (Exception e){
                      throw new RuntimeException();
                  }finally {
                      unlock(lockkey);
                  }
            });
        }

        //失败，返回过期时间
        //释放锁

        //7.返回
        return shop;
    }


    //尝试获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    //释放锁
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }


    //逻辑重建
    public void saveShop2Redis(Long id,Long expireSeconds){
        //1.查询店铺信息
        Shop shop = getById(id);
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY+id,JSONUtil.toJsonStr(redisData));
    }

    //更新商店操作
    @Override
    @Transactional    //事务，保证事务的一致性
    public Result update(Shop shop) {
        Long id = shop.getId();
        String key = CACHE_SHOP_KEY+id;
        if(id==null){
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(key);
        return Result.ok();
    }
}
